Lithium polymer batteries (LiPBs), as a next-generation secondary battery, have been used as a battery in an eco-friendly vehicle such as an electric vehicle or a hybrid vehicle. The lithium polymer battery (LiPB) is a secondary battery that uses a solid electrolyte having excellent ion conductivity. In a liquid electrolyte cell, an electrolytic solution may likely leak and an organic solvent used in the electrolytic solution is a flammable material, whereas a solid electrolyte cell such as the lithium polymer battery has an advantage in that the cell has no possibility (e.g., minimal) of leakage of an electrolytic solution and risk of explosion, has a low internal resistance and a high energy density, and does not cause a reduction in lifespan of the battery without full charging and full discharging since the cell does not have a memory effect.
However, in a substantially low temperature region, as a state of charge (SOC) decreases, the internal resistance of the battery rapidly increases, causing a discharge output to decrease. Since a driving condition of a vehicle is determined by an output based on the battery temperature and the SOC rather than limiting an output based on the SOC of the battery in the driving state of the vehicle, there is a need to increase the battery in a substantially low temperature state to a proper temperature (e.g., a predetermined temperature for the driving state) to secure power performance of the vehicle at the substantially low temperature.
When the battery is charged in the substantially low temperature state, overvoltage rising of an anode and a cathode is asymmetrically increased, such that compared with the charging at room temperature, charging capacity may be decreased and a cathode voltage may be decreased to a substantially low voltage. In particular, metal-like lithium is educed in the battery, and when this condition is repeated for a substantial period of time, the performance of the battery may deteriorate and an internal short-circuit may occur.
To efficiently use the lithium polymer battery (LiPB), and secure safety and durability life of the LiPB, there is a need to properly manage a use temperature of the battery. However, when a heater rapidly applies heat to increase the battery temperature, there may be a risk of fire, explosion, and the like, and therefore, a need exists for a system to efficiently control heat of the heater based on the temperature and peripheral condition of the battery.
As the current battery temperature raising system, a method for increasing the battery temperature by heating a fluid circulating a battery pack with a positive temperature coefficient (PTC) heater, a method for heating air around the battery by using a blanket type heater that surrounds a battery module, and the like have been previously developed.
The main performance of the battery temperature raising system depends on the short temperature rising time to rapidly improve the output of the battery at the lower temperature and the safety assurance to prevent a risk such as a fire from occurring in any situation. To shorten the battery temperature rising time, there is a need to decrease resistance of power supply to increase a heating value from the heater, and to secure the safety of the battery, there is a need to increase resistance of power supply to decrease the heating value from the heater.
However, according to the related art, when the heating value from the heater is increased unconditionally, the fire in the battery may occur in an abnormal situation, and particularly, a spark may occur due to a thermal deformation of the heater and the fire of the battery may occur due to the leakage of the flammable gas, and the like which are caused by an excessive battery temperature rising, which may lead to a risk of the overall vehicle. When the heating value from the heater is increased in consideration of only the shortening of the temperature rising time, it may be difficult to secure the safety of the battery due to the continuous heating during the failure of the temperature raising system.